I'd say for you the scale is definitely not necessary. You are clearly under the limit and will check anyway. For your husband it may be good enough to weigh the bag at home. If nothing gets added during the trip he should still be alright. If he does have something in addition, just put it in your bag (if you travel together).

My bathroom scale was around $50 is from Soehnle (German scale specialist) and is accurate to 100g. Not trade grade but definitely ok.

Another point is to simply lighten your luggage in other ways. Either take a lighter suitcase or make an effort with the packing list or both. Or offload some heavy things like books and electronics into your personal item bag or jacket pockets.

All that to say that the real question is not if they are accurate but if they are needed.

Till